Frontier was the name given to the first version of the Ethereum mainnet, which was released in July 2015 and used a proof-of-work (PoW) consensus mechanism. Frontier was a simple structure that got the network up and running. It only offered a command line interface (CLI) for mining ether (ETH) and uploading and executing smart contracts. Frontier and the Ethereum network were launched between the founding of Ethereum in 2013 and the subsequent mainnet launch in 2015.